Shortly after he landed on Canadian soil for the first time as president, Donald Trump was warmly greeted by Justin Trudeau and his wife, Sophie Grégoire Trudeau.

The trio lingered on the podium, chatting comfortably as they posed for photos at the start of the G7 summit in Quebec.

There was little hint of the acrimony that had filled Trump’s Twitter feed hours earlier as he had raged at Canada and its prime minister, laying bare escalating trade tensions that have seemingly pushed US-Canada relations to their lowest point in recent memory.

“Prime Minister Trudeau is being so indignant, bringing up the relationship that the U.S. and Canada had over the many years and all sorts of other things,” Trump tweeted on Thursday. “But he doesn’t bring up the fact that they charge us up to 300% on dairy – hurting our Farmers, killing our Agriculture!”

The tweet was part of tumultuous 24 hours or so in which Trump mused about terminating the North American Free Trade Agreement (Nafta), the pact that underpins roughly 2.5m Canadian jobs and the three-quarters of Canadian exports that go to the US, and railed at Canada’s use of import tariffs and production controls to protect its dairy sector.

Trump’s increased targeting of Canada appeared to begin earlier this year when he sought to portray it as a country of suave swindlers, said Christopher Sands, director of the Center for Canadian Studies at Johns Hopkins University.

“We lose a lot with Canada. People don’t know it. Canada is very smooth,” Trump told a gathering of state governors in February. “They have you believe that it’s wonderful. And it is. For them – not wonderful for us … So we have to start showing that we know what we’re doing.”

“That kind of annoyed Trump,” he said. “I don’t think he loves Trudeau but I think that early on they had a good rapport. Now he finds that Trudeau is undermining him in his own turf.”

Trump to Trudeau in testy tariff call: 'Didn't you guys burn down the White House?'

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Trade tensions escalated after the US announced an end to Canada’s exemption on steel and aluminum tariffs, one week after a reportedly testy phone call between the two leaders, in which Trump referenced the 1814 burning down of the White House by British troops to justify levying the tariffs against Canada on national security grounds.

Canada countered with retaliatory measures on C$16.6bn ($12.8bn) worth of goods and a tougher line from Trudeau. After more than a year of carefully avoiding any criticism of the US president, Trudeau slammed the president’s decision. “We have to believe that at some point their common sense will prevail,” he told reporters. “But we see no sign of that in this action today by the US administration.”

The result is the kind of sparks that have probably existed between US and Canadian leaders throughout history, but which are rarely aired in public, said Sands. “Nixon famously called Justin Trudeau’s father an asshole and Trudeau zinged back – but it was all behind the scenes and it came out years later.”

“It is all posturing within the context of the Nafta negotiations,” said Dunniela Kaufman, a Canadian trade lawyer based in Washington. “I think Trump thought that he would arrive and the Canadians would play ball, that they would negotiate with him and get to where they needed to get.”

But the talks have stalled after the Canadians refuse to budge on two key issues: a sunset clause that would allow any of the signatories to quit the pact after five years and binding dispute mechanisms.

Trump had hoped the US metal tariffs would force Canada’s hand. Instead the country shot back with retaliatory measures, she said. “So I think he’s frustrated that Canada didn’t do that.”

Officials on both sides of the border have downplayed any notion of a feud brewing between the longstanding allies. “I regard this as much like a family quarrel,” Larry Kudlow, Trump’s chief economic adviser, told reporters this week. “I’m always the optimist, I believe it can be worked out, and I’m always hopeful on that point.”